Floral tributes are left at the family home of Gurmail Singh who died after a robbery at his shop in Cowcliffe, near Huddersfield. Photograph: John Giles/PA

He has been described as an open-all-hours shopkeeper, a man who was admired by his elderly customers who he would go the extra mile for, delivering groceries to the homes of the most vulnerable and frail.

But on Saturday evening Gurmail Singh, 63, died after he was struck over the head with a sledgehammer during a robbery involving four male youths at the Cowcliffe Convenience Store in Cowcliffe, near Huddersfield, West Yorkshire.

They escaped after grabbing a small amount of chewing gum, cigarettes and cash from the till. The father of three died in hospital seven hours later. Two days earlier, his shop had been robbed by youths who the police "strongly suspect" are the same ones who struck on Saturday.

It emerged that the robbers were disturbed by David Singh, who is not related to the victim. He was outside a nearby pub when he saw two youths in hooded tops outside the shop. He went to investigate and saw two other youths inside rifling through cigarettes. He held the door shut to prevent them leaving, despite being threatened with a hammer and having glass from broken bottles thrown at him.

Today Detective Superintendent David Pervin, leading the inquiry, described the murder as an "absolute tragedy and shame". He appealed to the local community to come forward with information that would lead to the killers.

Gurmail Singh, 63. Photograph: West Yorkshire police/PA

Police believe that the shopkeeper had put up some resistance and "because of that he was injured and murdered".

"I believe they got away with very little," Pervin said. "They dropped one or two packets of cigarettes, some coin bags and some chewing gum. This is a murder they've committed, an awful murder and they have got away with next to nothing."

He added: "Mr Singh worked extremely hard. He was well liked by everyone. He is described as extremely jolly, would do absolutely anything for anyone. There was no need for this to happen."

Pervin described how a group of people outside the pub opposite "very bravely" tackled two youths who ran from the back of the shop. He said one man rugby-tackled an offender, while another man tripped up a second suspect. But the youths got away. Singh was found on the floor, unconscious and with very serious head injuries.

The four suspects are described as in their late teens or early 20s. They were wearing black hooded tops and black or dark trousers.

The shopkeeper had been involved in a similar incident on Thursday night when two young men with the same descriptions tried to snatch cigarettes and he tried unsuccessfully to stop them.

Pervin said Singh, who arrived in the UK in 1963, and leaves a wife, two adult sons and a daughter, had celebrated his 63rd birthday on Friday. For the last five years he opened the store 15 hours a day – from 6am to 9pm, seven days a week – and even delivered papers before opening.

David Singh, who tried to stop the robbers, said: "All I could think about was keeping them inside long enough for the police to arrive. One lad was hitting the door with a lump hammer, kicking it and hitting it with bottles. There was glass all over me."

The leader of Kirklees council, Mehboob Khan, paid tribute to his former neighbour whom he described as extremely hard-working and a man who would not hurt a fly.

The pair had known each other for 19 years, said Khan. "I got to see him on a daily basis and he would come to me as his councillor and discuss issues with me. He was a family-orientated man and very polite. He was very popular in the area, particularly with his elderly customers. He was always putting other people first and thinking of his family. He was a real pillar of the community."

"I remember very recently he went out in the snow to deliver essential groceries to them."

Barbara Batten said that Gurmail Singh used to visit her late mother's house if she was unable to get out.

"In the winter, if the weather was too bad for her to get out, she would telephone and he would deliver to her door," she said. "Both he and his wife were very kind to her. Mr Singh was a real gentleman and will be sadly missed."

A postmortem took place today, while an emergency meeting of the Sikh community in Huddersfield took place at the police station yesterday evening. The Sikh community and Singh's family are said to be devastated by the loss.